Miscellaneous
Need a fancy CPU cooler or a sound card? You've come to the right place. This is where we talk about components that, while not always strictly necessary, can improve a build in very real ways.

Aftermarket CPU coolers
Since Intel's Core i5-6600K and Core i7-6700K don't ship with stock coolers, you'll want to pick one from our selections below. Haswell-E builders will need to pick out a cooler, as well. Be careful to note your case's maximum CPU cooler height before buying one of these, as tall tower heatsinks need a lot of space.

The coolers listed below are all more powerful and quieter than the stock Intel solutions. The more affordable ones are conventional, tower-style designs with large fans, while the higher-priced Corsair H-series and Cooler Master Nepton units are closed-loop liquid coolers that can be mounted against a case's exhaust vents.

As far as entry-level coolers go, it doesn't get much better than Cooler Master's Hyper 212 Evo. This is a very popular choice with over 6,000 five-star reviews at Newegg.

A more effective option for those looking to overclock might be Phanteks' PH-TC12DX, which comes with twin fans. The reviewers at TechPowerUp found that the TC12DX has substantial cooling power for its size—it held an overclocked Sandy Bridge-E chip to just 65° C under a Prime95 load. It also tops out at just 47 dBA with its fans spinning at maximum speed. Those are quite respectable numbers for this cooler's $50 price tag.

For cases that can't swallow the Hyper 212 Evo or the PH-TC12DX, consider the Cooler Master Hyper D92. It's much quieter under load than the boxed heatsink that ships with Intel CPUs, and its 5.5" (140 mm) height works well with many microATX and some Mini-ITX cases.

For builds where more extreme overclocking is in the cards, we think liquid coolers are the best bet. These coolers are entirely self-contained and require no special setup. You simply mount them against a case's exhaust vent with the fan blowing through the radiator fins, and the closed-loop liquid cooling system takes care of everything. Corsair's H60 is a good candidate for small cases that can only accomodate a slim radiator with one fan.

For beefier builds, we're fans of Cooler Master's Nepton 120XL and Nepton 240M all-in-one liquid coolers. The Nepton 120XL has a thick 120-mm radiator paired with two push-pull fans, while the 240M sports a humongous 240-mm heat exchanger. Both of these coolers feature Cooler Master's quiet Silencio FP 120-mm fans, and they both use the same pump head and mounting system. Pick whichever one fits your case of choice.

All of these liquid coolers take next to no space around the CPU socket, since their radiators mount to the case wall. For that reason, they're ideal for something like a Haswell-E system packed with tall memory modules. In fact, we very much recommend liquid cooling for any Haswell-E build, given how crowded the area around the socket tends to be.

Sound cards
A lot of folks are perfectly content with their motherboard's integrated audio these days. However, each time we conduct blind listening tests, even low-end discrete sound cards wind up sounding noticeably better than integrated audio. That's with a pair of lowly Sennheiser HD 555 headphones, too, not some kind of insane audiophile setup. If you're using halfway decent analog headphones or speakers, a sound card is a worthwhile purchase.

It's fine to stick with motherboard audio if you use digital speakers or USB headphones, since those handle the analog-to-digital conversion themselves. That said, even with digital speakers, the sound cards we recommend below will do things that typical onboard audio cannot, such as surround sound virtualization and real-time Dolby multi-channel encoding.

The Xonar DSX and Xonar DX can both drive analog headphones or 7.1-channel speaker setups (either analog or digital). In our blind listening tests performed with analog headphones, these two cards sounded very similar. The DSX is the more affordable of the two, but the DX gets you Dolby Headphone virtualization in exchange for a small price premium.